: I just replaced old galvanized hot and cold water feed pipes to a bathroom with PEX, fed from a section of the house that has copper. Relaced feed to tub w shower, toilet and basin. Flow was terrible - now is great.

: BUT a bad water hammer (banging) has developed, when either hot or cold water is turned on or off on any of the devices on the PEX lines. Also occurs when turned on or off at the sink right next to the PEX line, but served on existing copper.

: It is much worse on turing water off than turing on. Typically get two bangs within a second.

: Have installed expansion chambers on both hot and cold near tub controls. Made of 14" long 3/4" diameter copper pipe t-ed into PEX.

: Sounds seems to be coming from tub control, which is why I installed expansion chambers near there. Tub control is a 9 year old American Standard single lever control with pressure balance. I called American Standard - they suggested that I reduce the pressure to the whole house. Thanks!

: They also suggested that I install a pressure rgulator. This might be more palatable because it shouldn't reduce the flow that much just limit the pressure. The other idea I had was to try a very large expansion tube to try and really smooth the pressure changes.

: Any suggestions would be appreciated.

: Thanks, John

Flow is a result of pressure. When the pressure is high enough to increase the velocity of the flow to the point of causing hammer, the best solution is to reduce the pressure. If you're on 'city' water, the best way to do that is with a pressure reducing valve. Water hammer is damaging to the plumbing and fixtures, even when you can't hear it or believe it's loud enough to do something about it. IMO residential water pressure shouldn't be much above 65 psi, which is more than adequate for most houses.